In this type of cartridge, the thermostatic regulation is generally obtained by means of an expandable thermostatic element comprising firstly a piston normally fixed with respect to the hollow external casing of the cartridge and secondly a body secured to a regulation slide valve. This slide valve is movable with respect to the casing of the cartridge so as to inversely vary the cross sections of flow of the two fluids, referred to as “hot fluid” and “cold fluid”, supplying the cartridge with a view to mixing these fluids in variable proportions in order to obtain, downstream from the slide valve, a fluid referred to as “mixed fluid”, which flows along a thermosensitive part of the thermostatic element and leaves the cartridge. By modifying the position of the piston with respect to the casing, generally by means of an ad hoc adjustment mechanism, the thermostatic regulation temperature is fixed, that is to say the balancing temperature around which the temperature of the mixed fluid is regulated. An example of this type of cartridge is provided by EP-A-1 496 415, on which the preamble of the accompanying claim 1 is based.
In practice, the movements of the slide valve between two extreme positions, respectively for which the flow of hot fluid is completely closed and the flow of cold fluid is completely closed, are around a few millimeters only in cartridges of standard dimensions. As a result the maximum flows of hot fluid and cold fluid that can be admitted into these cartridges are limited. This limitation of the flows of hot fluid and cold fluid is accentuated by the fact that the arrival of these fluids at the regulation slide valve is concentrated on limited respective portions of the external periphery of the slide valve: this is because the hot and cold fluids, in having been brought to the slide valve, have passed through the casing of the cartridge, while taking account of the environment, more or less constrained, in which the cartridge is to be installed. In order to get round this difficulty, hollowing out, in the internal face of the cartridge casing, peripheral grooves for supplying the slide valve with fluid is known, the hot fluid and cold fluid inlets emerging respectively in such grooves. However, in practice, this solution remains expensive to implement and especially it tends to reduce the inside diameter of the casing in favour of its thickness for hollowing out the aforementioned grooves, which in particular limits the outside diameter of the slide valve and thereby limits the maximum flows of fluid that can be regulated by this slide valve. Moreover, in some cases and/or for some cartridge casings, the presence of such internal grooves cannot be envisaged technically.